38
PRE-RESTORATION ANALYSIS OF DISCHARGE, SEDIMENT TRANSPORT RATES, WATER QUALITY, AND LAND-USE IMPACTS IN THE BAYOU LA BATRE WATERSHED, MOBILE COUNTY, ALABAMA
PRE-RESTORATION ANALYSIS OF DISCHARGE,
SEDIMENT TRANSPORT RATES, WATER QUALITY,
AND LAND-USE IMPACTS IN
THE BAYOU LA BATRE WATERSHED,
MOBILE COUNTY, ALABAMA
ii
PRE-RESTORATION ANALYSIS OF DISCHARGE,
SEDIMENT TRANSPORT RATES, WATER QUALITY,
AND LAND-USE IMPACTS IN
THE BAYOU LA BATRE WATERSHED,
MOBILE COUNTY, ALABAMA
By
Marlon R. Cook,
Polyengineering, Inc.
Funding for this project was provided by the
Mobile Bay National Estuary Program
August 2016
iii
TABLE OF CONTENTS
Introduction .........................................................................................................................1
Acknowledgments ...............................................................................................................1
Project area...........................................................................................................................1
Project monitoring strategy and site conditions ...................................................................3
Land use ...............................................................................................................................3
Stream flow conditions ........................................................................................................6
Specific conductance ...........................................................................................................8
Turbidity ..............................................................................................................................9
Sedimentation ....................................................................................................................12
Sediment loads transported by project streams ............................................................13
Suspended sediment ...............................................................................................13
Bed sediment ..........................................................................................................17
Total sediment loads ..............................................................................................18
Nutrients .............................................................................................................................20
Nitrate ....................................................................................................................20
Phosphorus .............................................................................................................21
Dissolved oxygen ...............................................................................................................23
Conclusions and sources of water-quality impacts ............................................................24
References cited .................................................................................................................29
ILLUSTRATIONS
Figure 1. Bayou La Batre project area ..............................................................................2
Figure 2. Bayou La Batre watershed, streams, and monitored sites .................................4
Figure 3. Land use classifications for the Bayou La Batre area ........................................5
Figure 4. USGS 7.5-minute topographic map of a selected area of the Bayou
La Batre watershed, showing stream gradients and anthropogenic
features ...............................................................................................................7
Figure 5. Conductivity and discharge relationships for samples collected at
sites BLB1 and BLB2 ......................................................................................10
iv
Figure 6. Turbidity and TSS relationship showing difference between fresh-
and saline-water samples at site BLB1 ............................................................11
Figure 7. Average turbidity and discharge relationships for Bayou La Batre
monitored sites .................................................................................................11
Figure 8. Turbidity and TSS relationship for fresh-water samples from Carls
Creek site BLB3 ...............................................................................................14
Figure 9. Average annual daily discharge and suspended sediment loads for
Bayou La Batre monitored sites .......................................................................16
Figure 10. Comparisons of total sediment geologic erosion rate loads with
estimated total sediment loads for monitored Bayou La Batre
watersheds ........................................................................................................18
Figure 11. Comparison of total sediment loads for streams in Baldwin and
Mobile Counties ...............................................................................................19
Figure 12. Relationships of measured nitrate with measured conductance and
discharge at site BLB3 (Carls Creek man-made channel at Arnette
Street) ...............................................................................................................22
Figure 13. Relationship of nitrate and discharge at site BLB4 (Carls Creek
natural channel at Arnette Street) ....................................................................22
Figure 14. Carls Creek channel bifurcation just south of Padgett Switch Road ................25
Figure 15. Sources of water quality impacts identified by field observations ...................27
Figure 16. Turbid runoff from row-crop fields in unnamed tributary to
Hammar Creek at Tom Waller Road immediately after a rain event ..............28
TABLES
Table 1. Stream-flow characteristics for monitored sites in the
Bayou La Batre watershed .................................................................................8
Table 2. Measured specific conductance values for the Bayou La Batre
monitoring sites ..................................................................................................9
Table 3. Measured discharge, turbidity, and TSS and estimated suspended
sediment loads in monitored streams in Bayou La Batre watershed ...............15
Table 4. Dissolved oxygen measured in monitored streams in the Bayou La
Batre watershed ................................................................................................24
Appendix A—Field and analytical data .............................................................................31
1
INTRODUCTION
Commonly, land-use and climate are major contributors to non-point source
contaminants that impact surface-water quality. In parts of Baldwin and Mobile Counties,
population growth and economic development are critical issues leading to land-use
change. When combined with highly erodible soils and Alabama’s coastal climate,
characterized by cyclonic storms that produce high intensity rainfall events, deleterious
water-quality and biological habitat impacts can be severe. Previous investigations of
sediment transport and general water quality have shown dramatic increases in sediment
loading and loss of biological habitat in streams downstream from areas affected by rapid
runoff and resulting erosion from particular types of land uses. Other areas are virtually
unimpacted by land-use change and are characterized by natural landscapes dominated by
forests and wetlands. Results of these investigations are valuable in quantifying impacts
so that limited regulatory and remedial resources may be focused to remediate problem
areas or to preserve relatively pristine watersheds.
The purpose of this investigation is to assess general hydrogeologic and water
quality conditions and to estimate sediment loads for Bayou La Batre and its tributaries.
These data will be used to quantify water quality impacts and to support development of
a watershed management plan, designed to preserve, protect, and restore the Bayou La
Batre watershed.
ACKNOWLEDGMENTS
Ms. Roberta Swann, Director; Ms. Amy Newbold, Deputy Director; and Mr. Tom
Herder, Watershed Protection Coordinator, Mobile Bay National Estuary Program,
provided administrative and coordination assistance for the project; Mr. Bruce Bradley,
President, Polyengineering, Inc., provided administrative and technical assistance; Mr.
Christopher Warn, Senior Project Manager, Dewberry, provided coordination for the
watershed management plan.
PROJECT AREA
The Bayou La Batre watershed covers 19,584 acres (30.6 square miles (mi2) (US
Geological Survey (USGS), 2016) in southern Mobile County (fig. 1). The project area
includes monitoring sites on three tributaries and the main stem of Bayou La Batre.
Bayou La Batre flows southwestward from its headwaters about one and three quarters
miles northeast of the town of Bayou La Batre to its mouth in Portersville Bay in the
2
Mississippi Sound (fig 2). Elevations in the project area vary from about 15 feet above
mean sea level (ft MSL) at the headwaters to sea level at the mouth. The three monitored
tributaries include two unnamed streams, and Carls Creek. Carls Creek is the largest
subwatershed, containing 13,248 acres (20.7 mi2) (USGS, 2016) and two tributaries;
Hammar Creek and Bishops Manor Creek with maximum elevations of about 140 ft
MSL.
Figure 1.— Bayou La Batre project area.
3
PROJECT MONITORING STRATEGY AND SITE CHARACTERISTICS
The monitoring strategy employed for the Bayou La Batre project was to collect
water samples at each site over a wide range of discharge from base flow to high flow for
analyses of total suspended solids, nitrate, and total phosphorus, and constituent load
estimation. A number of factors, including site accessibility in a rural, wetlands
dominated setting, extensive wetlands and tidal influence that constrains stream flow and
impacts water chemical character, and selection of sites as far downstream as possible,
were considered during selection of monitoring sites.
Site BLB1 is on the main stem of Bayou La Batre at Wintzell Avenue, the most
downstream access point, flowing southwestward, 2.5 mi from the mouth (latitude (lat)
30.40572, longitude (long) -88.24798). The watershed upstream from site BLB1 covers
14,848 acres (23.2 mi2 ) (USGS, 2016) (fig. 2).
Site BLB2 is on an unnamed tributary on the northwest side of the town of Bayou
La Batre at the Little River Road crossing (lat 30.40706, long -88.25691). The watershed
upstream from site BLB2 covers 3,200 acres (5.0 mi2 ) (USGS, 2016) (fig. 2).
Sites BLB3 and BLB4 are on Carls Creek, which is formed by two tributaries,
Hammar Creek and Bishops Manor Creek, that join to form Carls Creek 2.5 miles
upstream from Site BLB3 (fig. 2). One mile downstream from the tributary confluence,
the Carls Creek channel splits (fig. 2). Site BLB3 is on a man-made channel at the
Arnette Street crossing, about 1.5 miles downstream from the split (lat 30.41066, long -
88.24566) (fig. 2). The man-made channel rejoins the natural channel 400 ft downstream
from site BLB3 and flows into Bayou La Batre 2,600 ft downstream from the site (fig.2).
Site BLB4 is on a natural channel at the Arnette Street crossing (lat 30.41060,
long -88.24496), 150 ft east of the BLB3 site and 1.5 mi downstream from the Carls
Creek channel split. The watershed upstream from sites BLB3 and BLB4 contains 13,248
acres (20.7 mi2 ) (USGS, 2016) (fig. 2).
LAND USE
Land use is directly correlated with water quality, hydrologic function, ecosystem
health, biodiversity, and the integrity of streams and wetlands. Land-use classification for
the project area was calculated from the USDA National Agricultural Statistics Service
2013 Alabama Cropland Data Layer (NASS CDL) raster dataset. The CDL is produced
using satellite imagery from the Landsat 5 TM sensor, Landsat 7 ETM+ sensor, the
4
Spanish DEIMOS-1 sensor, the British UK-DMC 2 sensor, and the Indian Remote
Sensing RESOURCESAT-1 (IRS-P6) Advanced Wide Field Sensor (AWiFS) collected
during recent growing seasons (USDA, 2013). Figure 3 shows land use, subdivided into
17 classified types defined as developed, forested, grassland, wetlands, barren areas, open
water, and agriculture, subdivided into eight specific crops (fig. 3).
Bayou La Batre watershed
Hammar Creek
Bishop Manor Creek Carls Creek
Bayou La Batre
BLB1 BLB4
BLB3
BLB2
Figure 2.—Bayou La Batre watershed, streams, and monitored sites.
5
The dominant land use category in the Bayou La Batre watershed is pasture/hay
and wetlands (fig. 3). Wetlands are important because they provide water quality
improvement and management services such as: flood abatement, storm water
management, water purification, shoreline stabilization, groundwater recharge, and
streamflow maintenance. The next largest land use categories are evergreen and mixed
forest and surprisingly, developed land (fig. 3). Developed land in the northern part of the
watershed (Carls Creek and tributaries) is dominated by residential development,
Figure 3.-Land use classifications for the Bayou La Batre area.
6
primarily along roadways (fig. 3). Developed land in the southern part of the watershed is
primarily related to the town of Bayou La Batre (fig. 3). Agriculture is a dominant land
use in the headwaters of Carls Creek tributaries (fig. 3). Crops consist of peanuts,
soybeans, corn, cotton, and pecans. Land uses and their specific impacts are discussed in
detail in the Conclusions and Sources of Water-Quality Impacts section of the report.
STREAM FLOW CONDITIONS
Numerous streams in Baldwin County exhibit flashy discharge due to relatively
high topographic relief and land-use change. Most streams in the Dog River watershed, in
and near the city of Mobile, are also flashy, with relatively high velocities and an average
stream gradient of 48 ft/mi, due to channelization and urbanization. However, the
character of stream flows in the Bayou La Batre watershed are quite different and
influenced by a number of natural and anthropogenic factors. Stream channels in the
northern part of the watershed, consisting of Carls Creek tributaries (Bishop Manor and
Hammar Creeks) are characterized by relatively high elevation (maximum 140 ft MSL,
average 48 ft MSL), with topography that decreases in relief from north (upstream) to
south (downstream). The tributary flood plains are dominated by wetlands, channels that
are in part, anastomosing, and stream gradients that decrease from upstream to
downstream in three zones from 33 to 21 to 10 ft/mi (fig. 4). Prior to 1956, anthropogenic
impacts influencing stream discharge in the downstream part of Carls Creek, include a
relief channel 1.6 miles long along Padgett Switch Road and eight man-made channels
constructed to drain a 300-acre low area between the Carls Creek relief channel and
Padgett Switch Road (fig. 4). After 1985, much of the drained area was filled to construct
Lucille Zirlott Park, a number of businesses, and a medical center along Padgett Switch
Road. However, one of the drainage ditches and the Carls Creek relief channel remain.
Other anthropogenic impacts to stream flow include a 6,800-foot-long constructed
channel in the headwaters of Bayou La Batre, east of the town of Bayou La Batre (fig. 4).
The Carls Creek natural channel, monitored unnamed tributary, and Bayou La Batre are
in the Alabama Coastal Zone, where they flow through the eastern extent of Grand Bay
Swamp, and have an average gradient of 7 ft/mi. The Carls Creek man-made channel has
a gradient of 11 ft/mi. Conductance values for a number of monitoring events indicate
tidal influence on volume and quality of stream flow.
7
Figure 4.—USGS 7.5-minute topographic map of a selected area of the Bayou La Batre watershed,
showing stream gradients and anthropogenic features.
Carls Creek channelized drainage
Bayou La Batre channelization
High stream gradients
Moderate stream gradients
Low stream gradients
8
A wide range of discharge events are required to adequately evaluate hydrologic
conditions in Bayou La Batre. Table 1 shows that sampling occurred in the Bayou La
Batre watershed during discharge conditions from base flow to flood. For example,
minimum discharge measured for Carls Creek at Arnette Street (site 3) was 10.3 cfs
(January 13, 2016) and the maximum was 444 cfs, measured on January 21, 2016 .
Average daily discharge for each monitored stream is also required to adequately
estimate constituent loading. Discharge data collected at the USGS stream gaging site
02471078, Fowl River at Half Mile Road, near Laurendine, Alabama was used as a basis
for average daily discharge estimation for each monitored stream.
Table 1.—Stream-flow characteristics for monitored sites in the
Bayou La Batre watershed.
Monitored
site
Average
discharge
(cfs)
Maximum
discharge
(cfs)
Minimum
discharge
(cfs)
Average discharge
per unit area
(cfs/mi)
Average
stream flow
velocity
(ft/s)
Stream gradient
(ft/mi)
1 1,131 1,9371 4391 49 0.6 3.2
2 162 2301 110 35 0.5 8.6
3 131 444 10 1.1
4 160 2811 17 0.9
3 and 4 291 725 27 14 1.0 16.3 1TI- tidal influence
SPECIFIC CONDUCTANCE
Surface water in each project watershed is characterized by a unique specific
conductance (SC) (microseimens/centimeter (µS/cm)) profile based on physical and
chemical properties. The variability of SC is influenced by differences in stream
temperature, discharge, total dissolved solids, local geology and soil conditions, and ionic
influxes from nonpoint sources of pollution or from seawater in reaches of streams with
tidal influence. Streams without significant contaminant sources exhibit increased SC
values with decreasing discharge due to increasing volumes of relatively high SC
groundwater inflow and decreased SC with increasing discharge due to increasing volumes
of relatively low SC runoff. The opposite SC character is exhibited for streams with
significant contaminant sources where relatively high conductance runoff causes
increasing SC with increasing discharge. Fluctuations of SC in streams with tidal influence
correspond to tidal cycles with relatively high SC (salt water) at high tide and relatively
low SC (fresh water) at low tide. However, the relationship between runoff, discharge, tidal
9
cycles, and conductivity can be extremely complex, as was observed in data collected at
sites BLB1 and BLB2. Table 2 shows SC in monitored streams in the Bayou La Batre
watershed. Figure 5 shows the relationship between discharge and conductivity for samples
collected at sites BLB 1 and 2. BLB1 samples are grouped by relatively high discharge and
low conductivity and relatively low discharge and high conductivity. BLB2 samples are
grouped by relatively high and low conductivity, but discharge does not appear to have an
influence. This is most likely due to the dominance of wetlands and marsh upstream from
site BLB2 that limits surface-water runoff and maximizes groundwater contributions to
flow. However, it is clear that tidal cyclicity is a major influence on the chemical character
of these waters.
Table 2.—Measured specific conductance values for the Bayou La Batre
monitoring sites.
Monitoring
site
Maximum
conductivity
(µS/cm)
Minimum
conductivity
(µS/cm)
Average
conductivity
(µS/cm)
1 22,100 101 11,880
2 21,700 42 9,982
3 630 39 230
4 1,690 37 388
TURBIDITY
Turbidity in water is caused by suspended and colloidal matter such as clay, silt,
finely divided organic and inorganic matter, and plankton and other microscopic
organisms (Eaton, 1995). Turbidity is an expression of the optical property that causes
light to be scattered and absorbed rather than transmitted with no change in direction or
flux level through the stream (Eaton, 1995). Turbidity values measured in nephlametric
turbidity units (NTU) from water samples may be utilized to formulate a rough estimate
of long-term trends of total suspended solids (TSS) and therefore may be used to observe
trends in suspended sediment transport in streams. This relationship is more complex in
estuaries and streams with tidal influence, as is the case for streams in the Bayou La
Batre watershed. Turbidity and TSS in marine settings originate from organic and
10
inorganic material. Salinity of the ocean or estuary will cause suspended solids to
aggregate, or combine. As the aggregate weight increases, the solids begin to sink and
will settle on the seafloor or estuary bottom. This effect causes greater water clarity than
is observed in most lakes and rivers. The higher the salinity, the greater the effect. In
estuaries and tidal streams, turbidity values may be consistently high, due to the constant
resuspension of settled solids as tides move in and out (Fondriest Environmental, Inc.,
2014). However, turbidity and TSS in tidally influenced streams in the Bayou La Batre
watershed correlate differently, depending on whether the samples are fresh or saline (fig.
6). Samples from Bayou La Batre streams with elevated conductivity (saline water)
resulting from tidal influence, on average, have 43 percent higher TSS concentrations
than fresh-water samples with the same turbidity values. Figure 6 shows fresh-water and
saline-water turbidity and TSS correlations.
10
100
1,000
10,000
100,000
0 500 1,000 1,500 2,000
Co
nd
uct
ivit
y
Discharge BLB1 BLB2
Figure 5.—Conductivity and discharge relationships for samples collected at
sites BLB1 and BLB2.
11
Analyses of turbidity and stream discharge provide insights into hydrologic, land-
use, and general water-quality characteristics of a watershed. Average measured turbidity
and discharge, shown in figure 7, illustrates that generally, site BLB3 (channelized part of
Carls Creek at Arnette Street) has the highest turbidity to discharge ratio (0.4 NTU/cfs),
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60 70
TSS
(mg/
L)
Turbidity
saline water
fresh water
0
200
400
600
800
1000
1200
0 5 10 15 20 25 30 35 40 45 50
Dis
char
ge (
cfs)
Turbidity (NTU) BLB1 BLB2 BLB3 BLB4
Figure 6.—Turbidity and TSS relationship showing difference between
fresh- and saline-water samples at site BLB1.
Figure 7.—Average turbidity and discharge relationships for Bayou La Batre
monitored sites.
12
site BLB 4 (natural channel of Carls Creek at Arnette Street) is 0.1 NTU/cfs, site BLB2
(unnamed tributary at Little River Road) is 0.04 NTU/cfs, and site BLB1 (BLB at
Wintzel Avenue) has the lowest (0.02 NTU/cfs).
Commonly, excessive turbidity is closely tied to land uses that cause land
disturbances that lead to erosion or to land uses that cause excessive runoff. Field
observation indicate that a number of row crop fields in the headwaters of Bishop Manor
Creek have intermittent drainage channels with no vegetative buffers. Although a
majority of the monitoring data for Carls Creek (the largest tributary watershed in the
Bayou La Batre system) was collected in the downstream part of the watershed in order
to estimate constituent loading, additional data were collected at upstream sites to
determine tributary and headwaters contributions to downstream water quality. Storm
impacted flows were monitored in early August 2016 in the Bishop Manor and Hammar
Creeks watershed. Turbidity for Bishop Manor Creek, 1.8 mi upstream from the
confluence with Hammar Creek (Bishop Manor Creek at Argyle Road) was 114 NTU
and for Hammar Creek, 1.2 mi upstream from the confluence with Bishop Manor Creek
(Hammar Creek at 3 Mile Road) was 44 NTU. The highest turbidity measured during the
project period was 375 NTU at an unnamed tributary to Hammar Creek at Tom Weller
Road. This is a headwaters tributary, where part of the stream flows through row crop
fields with no vegetative buffer.
SEDIMENTATION
Sedimentation is a process by which eroded particles of rock are transported
primarily by moving water from areas of relatively high elevation to areas of relatively
low elevation, where the particles are deposited. Upland sediment transport is primarily
accomplished by overland flow and rill and gully development. Lowland or flood plain
transport occurs in streams of varying order, where upland sediment joins sediment
eroded from flood plains, stream banks, and stream beds. Erosion rates are accelerated by
human activity related to agriculture, construction, timber harvesting, unimproved
roadways, or any activity where soils or geologic units are exposed or disturbed.
Excessive sedimentation is detrimental to water quality, destroys biological habitat,
reduces storage volume of water impoundments, impedes the usability of aquatic
recreational areas, and causes damage to structures.
13
Precipitation, stream gradient, geology and soils, and land use are all important
factors that influence sediment transport characteristics of streams. Sediment transport
conditions in the Bayou La Batre watershed are evaluated and quantified by tributary, in
order to evaluate factors impacting erosion and sediment transport at a localized scale. In
addition to commonly observed factors above, wetlands, vegetation, and tidal effects also
play prominent roles in sediment transport and overall water quality in the Bayou La
Batre watershed. Estimates of sediment loads for this assessment are based on measured
sediment and stream discharge. Therefore, a stream flow dataset composed of values
ranging from base flow to flood is desirable. Observed stream flow conditions are shown
in table 1.
Sediment loads in streams are composed of relatively small particles suspended in
the water column (suspended solids) and larger particles that move on or periodically
near the streambed (bed load). A pre-monitoring assessment of sediment characteristics
indicated that due to low elevation and topographic relief and extensive wetlands,
relatively little bed sediment was present in the streams at selected Fowl River
monitoring sites. Therefore, total sediment loads for all monitored sites were assumed to
be suspended.
SEDIMENT LOADS TRANSPORTED BY PROJECT STREAMS
The rate of transport of sediment is a complex process controlled by a number of
factors primarily related to land use, precipitation runoff, erosion, stream discharge and
flow velocity, stream base level, and physical properties of the transported sediment.
Deterrents to excessive erosion and sediment transport include wetlands, forests,
vegetative cover and field buffers for croplands, limitations on impervious surfaces, and a
number of constructed features to promote infiltration of precipitation and to store and
slow runoff. Currently, the Bayou La Batre watershed maintains a relatively healthy
hydrologic environment, characterized by a relatively rural setting, minimal row crop
agriculture, low topographic relief, abundant wetlands, anastomosing stream channels,
and forested flood plains. However, a number of anthropogenic impacts to stream flow
and water quality were identified in the Bayou La Batre watershed that require evaluation
and possible remediation (see Conclusions and Sources of Water-Quality Impacts section
of the report).
14
SUSPENDED SEDIMENT
The basic concept of constituent loads in a river or stream is simple. However, the
mathematics of determining a constituent load may be quite complex. The constituent
load is the mass or weight of a constituent that passes a cross-section of a stream in a
specific amount of time. Loads are expressed in mass units (tons or kilograms) and are
measured for time intervals that are relative to the type of pollutant and the watershed
area for which the loads are calculated. Loads are calculated from concentrations of
constituents obtained from analyses of water samples and stream discharge, which is the
volume of water that passes a cross-section of the river in a specific amount of time.
Suspended sediment is defined as that portion of a water sample that is separated
from the water by filtering. This solid material may be composed of organic and
inorganic particles that include algae, industrial and municipal wastes, urban and
agricultural runoff, and eroded material from geologic formations. These materials are
transported to stream channels by overland flow related to storm-water runoff and cause
varying degrees of turbidity. Figure 8 shows that turbidity and suspended sediment are
closely related in Carls Creek (site BLB3), where water is primarily fresh. Turbidity,
TSS, suspended sediment loads, and discharge values for all monitoring sites are shown
in table 2.
0
50
100
150
200
250
0 50 100 150 200 250 300 350
TSS
(mg/
L)
Turbidity (NTU)
Figure 8.—Turbidity and TSS relationship for fresh-water samples from Carls
Creek site BLB3.
15
Annual suspended sediment loads were estimated for Bayou La Batre monitored
streams using the computer regression model Regr_Cntr.xls (Regression with Centering)
(Richards, 1999). The program is an Excel adaptation of the U.S. Geological Survey
(USGS) seven-parameter regression model for load estimation in perennial streams
(Cohn and others, 1992). The regression with centering program requires total suspended
solids (TSS) concentrations and average daily stream discharge to estimate annual loads.
Although average daily discharge for project streams was not available from direct
measurement for the monitored sites, it was estimated by establishing a ratio between
periodic measured discharge in project streams and discharge values for the same times
obtained from USGS stream gaging site (02471078, Fowl River at Half Mile Road, near
Laurendine, Alabama). The USGS gaging site is 7.4 mi northeast of Bayou La Batre and
has similar hydrogeologic and hydrologic characteristics (Cook, 2014).
Concentrations of TSS in mg/L were determined by laboratory analysis of
periodic water grab samples. These results were used to estimate the mass of TSS for the
period of stream flow (July 2015 to July 2016). Site BLB1 (Bayou La Batre at Wintzell
Avenue), had a suspended sediment load of 22,277 tons per year (t/yr) (table 3). Site
BLB2 (unnamed tributary at Little River Road) and the combined load for sites BLB3
and BLB4 (Carls Creek at Arnette Street) had suspended sediment loads of 2,921 and
7,604 t/yr, respectively. Figure 9 shows estimated average annual daily discharge and
suspended sediment loads, which shows that generally, increased discharge results in
increased suspended sediment loads for Bayou La Batre monitored sites.
Table 3.—Measured discharge, turbidity, and TSS and estimated suspended sediment
loads in monitored streams in the Bayou La Batre watershed.
Monitored
site
Average
Discharge
(cfs)
Average
turbidity
(NTU)
Maximum
turbidity
(NTU)
Average
TSS
(mg/L)
Maximum
TSS
(mg/L)
Estimated
suspended
sediment load
(t/yr)
Estimated
normalized
suspended
sediment load
(t/mi2/yr)
1 1,131 26 58 16 31 22,277 960
2 162 20 35 12 17 2,921 622
3 131 47 122 28 100
4 160 21 42 9 26
3&4
combined 291 34 122 37 106 7,604 367
16
For comparison with other watersheds in Mobile County, the largest suspended
sediment loads in the Dog River watershed were urban streams, Eslave Creek, Spencer
Branch, and Spring Creek with 10,803, 5,970, and 5,198 tons per year (t/yr), respectively
(Cook, 2012) and Fowl River watershed streams, Dykes Creek and Fowl River with
1,139 and 795 t/yr, respectively (Cook, 2014). Discharge and watershed area are two of
the primary factors that influence sediment transport rates in the Bayou La Batre
watershed.
Normalizing suspended loads to unit watershed area permits comparison of
monitored watersheds and negates the influence of drainage area size and discharge on
sediment loads. Normalized loads in the Bayou La Batre watershed are 960 t/mi2/yr for
Bayou La Batre site BLB1 (Bayou La Batre at Wintzell Avenue), 622 t/mi2/yr for site
BLB2 (unnamed tributary at Little River Road), and 367 t/mi2/yr for combined sites
BLB3 and BLB4 (Carls Creek at Arnette Street). These loads can be compared to the
largest normalized loads in Dog River streams, Spencer Branch, Spring Creek, and
Eslava Creek with 4,332 and 2,985, and 1,662 t/mi2/yr, respectively (Cook, 2012). The
0
100
200
300
400
500
600
700
0
5,000
10,000
15,000
20,000
25,000
BLB1 BLB2 BLB3-4
Dis
char
ge (
cfs)
Susp
end
ed s
edim
ent
(t/y
r)
Monitored site Suspended sediment Discharge
Figure 9.—Average annual daily discharge and suspended sediment loads for
Bayou La Batre monitored sites.
17
largest normalized loads in Fowl River streams were, unnamed tributary at Half Mile
Road, Dykes Creek, and unnamed tributary at Bellingrath Road with normalized loads of
303 and 271, and 128 t/mi2/yr, respectively. When the contribution of Carls Creek is
removed, the suspended sediment load upstream from site BLB1 (Bayou La Batre at
Wintzell Avenue) is 14,673 t/yr (5,869 t/mi2/yr). This is a substantial sediment load and
normally indicates significant upstream sources of sediment. However, it is suspected
that a significant part of the suspended sediment is related to the tidal resuspension of
sediment discussed previously.
BED SEDIMENT
Transport of streambed material is controlled by a number of factors including
stream discharge and flow velocity, erosion and sediment supply, stream base level, and
physical properties of the streambed material. Most streambeds are in a state of constant
flux in order to maintain a stable base level elevation. The energy of flowing water in a
stream is constantly changing to supply the required power for erosion or deposition of
bed load to maintain equilibrium with the local water table and regional or global sea
level. Stream base level may be affected by regional or global events including
fluctuations of sea level or tectonic movement. Local factors affecting base level include
fluctuations in the water table elevation, changes in the supply of sediment to the stream
caused by changing precipitation rates, and/or land use practices that promote excessive
erosion in the floodplain or upland areas of the watershed.
Bed load sediment is composed of particles that are too large or too dense to be
carried in suspension by stream flow. These particles roll, tumble, or are periodically
suspended as they move downstream. Traditionally, bed load sediment has been difficult
to quantify due to deficiencies in monitoring methodology or inaccuracies of estimating
volumes of sediment being transported along the streambed. This is particularly true in
streams that flow at high velocity or in streams with excessive sediment loads.
Due to a number of factors including relatively small areas of development or
land disturbance, limited sources of coarse-grained sediment, relatively low stream
gradients and stream flow velocities, and extensive wetlands that slow stream flow
velocities and detain sediment, no bed sediment was observed in Bayou La Batre streams
except the man-made channel upstream from site BLB3, which was too small to measure.
Therefore, all sediment loads are assumed to be suspended.
18
TOTAL SEDIMENT LOADS
Without human impact, erosion rates in the watershed, called the geologic erosion
rate, would be 64 t/mi2/yr (Maidment, 1993). Normalized sediment loads for all three
monitored watersheds were at least five times greater than the geologic erosion rate.
Calculated non-normalized geologic erosion rate loads are compared to total estimated
loads in figure 10.
Comparisons of sediment loads from other watersheds are helpful in determining
the severity of erosion problems in a watershed of interest. Estimates of total sediment
loads from Dog River site 2 (Spencer Branch at Cottage Hill Road in the city of Mobile)
(Cook, 2012), D’Olive Creek site 3 (D’Olive Creek at U.S. Highway 90 in Daphne)
(Cook, 2008), Tiawasee Creek site 7 (Tiawasee Creek upstream from Lake Forest)
(Cook, 2008), in Baldwin County, Joes Branch site 10 (at North Main Street in Daphne)
1,485
301
1,325
22,277
2,921
7,604
100
1,000
10,000
100,000
BLB1 BLB2 BLB3-4
Tota
l sed
imen
t lo
ad (
t/yr
)
Monitored site Geologic erosion rate load Estimated load
Figure 10.—Comparisons of total sediment geologic erosion rate loads with
estimated total sediment loads for monitored Bayou La Batre watersheds.
19
(Cook, 2008), Magnolia River site 4 (at U.S. Highway 98) (Cook, 2009), and Bon Secour
River site 3 (County Road 12 in Foley) (Cook, 2013) are compared to Bayou La Batre
monitored sites in figure 11. GSA estimated sediment loads for more than 60 streams in
Alabama. Fowl River at Half Mile Road (site FR2), three miles northeast of the Bayou La
Batre watershed, is an excellent reference site for streams in south Mobile County. Fowl
River, upstream from site FR2 is characterized by geology, topography, soils, wetlands,
and land use is similar to other streams in the region. The estimated sediment load at site
FR2 was 53 t/mi2/yr (20 percent lower than the geologic erosion rate).
52
4,332
1,987
692
35,813
112
1,531
960622
367
10
100
1,000
10,000
100,000
Tota
l sedim
ent
(t/m
i2/y
r)
Monitored site name and number
Figure 11.—Comparison of total sediment loads for streams in Baldwin and Mobile
Counties.
20
NUTRIENTS
Excessive nutrient enrichment is a major cause of water-quality impairment.
Excessive concentrations of nutrients, primarily nitrogen and phosphorus, in the aquatic
environment can lead to increased biological activity, increased algal growth, decreased
dissolved oxygen concentrations at times, and decreased numbers of species (Mays,
1996). Nutrient-impaired waters are characterized by numerous problems related to
growth of algae, other aquatic vegetation, and associated bacterial strains. Blooms of
algae and associated bacteria can cause taste and odor problems in drinking water and
decrease oxygen concentrations to eutrophic levels. Toxins also can be produced during
blooms of particular algal species. Nutrient-impaired water can dramatically increase
treatment costs required to meet drinking water standards. Nutrients discussed in this
report are nitrate (NO3-N) and phosphorus (P-total).
NITRATE
The U.S. Environmental Protection Agency (USEPA) Maximum Contaminant
Level (MCL) for nitrate in drinking water is 10 mg/L. Typical nitrate (NO3 as N)
concentrations in streams vary from 0.5 to 3.0 mg/L. Concentrations of nitrate in streams
without significant nonpoint sources of pollution vary from 0.1 to 0.5 mg/L. Streams fed
by shallow groundwater draining agricultural areas may approach 10 mg/L (Maidment,
1993). Nitrate concentrations in streams without significant nonpoint sources of pollution
generally do not exceed 0.5 mg/L (Maidment, 1993).
Water samples were collected from January through May 2016 at Bayou La Batre
monitoring sites for discharge events from base flow to bank full. Samples were analyzed
for nitrate. The critical nitrate concentration in surface water for excessive algae growth
is 0.5 mg/L (Maidment, 1993). All samples analyzed for nitrate at site BLB1 (Bayou La
Batre at Wintzell Avenue) were below detection limit of 0.3 mg/L. All samples analyzed
for nitrate from site BLB2 (unnamed tributary to Bayou La Batre at Little River Road)
were below detection limit or below the 0.5 mg/L nitrate criterion. Forty-three percent of
analytical results from samples collected at site BLB3 (man-made channel of Carls Creek
at Arnette Street) were below the detection limit, 43 percent were below the 0.5 mg/L
nitrate criterion, and 14 percent exceeded the 0.5 mg/L criterion. Analytical results for
samples collected at site BLB4 (natural channel of Carls Creek at Arnette Street) indicate
that 57 percent are below the detection limit and 29 percent are below the 0.5 mg/L
21
nitrate criterion, and 14 percent exceeded the 0.5 mg/L criterion. Lower concentrations of
nitrate are common in most streams during high flows due to dilution, resulting in
negative regressions when nitrate is plotted with discharge. However, nitrate and
discharge are not well correlated for streams in the Bayou La Batre watershed. Extremely
small nitrate concentrations at sites BLB1 (Bayou La Batre at Wintzell Avenue) and
BLB2 (unnamed tributary to Bayou La Batre at Little River Road) are likely caused by
dilution of runoff from the urban area of Bayou La Batre. Nitrate is poorly correlated
with discharge at site BLB3 but is relatively well correlated with conductivity (fig. 12).
Nitrate/conductivity correlations were the subject of an investigation by Iowa State
University researchers (Gali and others, 2012). The Iowa State University researchers
showed that in fresh water, conductivity and nitrate form positive regression correlations
and in some cases, conductivity could be used as a surrogate for nitrate. Nitrate has a
much better correlation with discharge at site BLB4, forming an expected negative
regression (fig. 13). These relationships indicate that dilution is a primary control of
nitrate concentrations in fresh-water streams.
Although concentrations are relatively small throughout the monitoring period,
elevated concentrations of nitrate in Carls Creek are expected, due to row crop
agriculture, cattle, and residential development in the headwaters of Bishop Manor Creek
and Hammar Creek (tributaries to Carls Creek) (fig. 3).
PHOSPHORUS
Phosphorus in streams originates from the mineralization of phosphates from soil
and rocks or runoff and effluent containing fertilizer or other industrial products. The
principal components of the phosphorus cycle involve organic phosphorus and inorganic
phosphorus in the form of orthophosphate (PO4) (Maidment, 1993). Orthophosphate is
soluble and is the only biologically available form of phosphorus. Since phosphorus
strongly associates with solid particles and is a significant part of organic material,
sediments influence water column concentrations and are an important component of the
phosphorus cycle in streams.
The natural background concentration of total dissolved phosphorus is
approximately 0.025 mg/L. Phosphorus concentrations as low as 0.005 to 0.01 mg/L may
cause algae growth, but the critical level of phosphorus necessary for excessive algae is
around 0.05 mg/L (Maidment, 1993). Although no official water-quality criterion for
22
phosphorus has been established in the United States, total phosphorus should not exceed
0.05 mg/L in any stream or 0.025 mg/L within a lake or reservoir in order to prevent the
development of biological nuisances (Maidment, 1993). In many streams phosphorus is
10
100
1000
0 0.1 0.2 0.3 0.4 0.5 0.6
Co
nd
uct
ance
an
d D
isch
arge
Nitrate (mg/L) Conductance Discharge
Figure 12.—Relationships of measured nitrate with measured conductance and
discharge at site BLB3 (Carls Creek man-made channel at Arnette Street).
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0 25 50 75 100 125 150 175 200 225 250 275 300
Nit
rate
(m
g/L)
Discharge (cfs)
Figure 13.—Relationship of nitrate and discharge at site BLB4 (Carls Creek
natural channel at Arnette Street).
23
the primary nutrient that influences excessive biological activity. These streams are
termed “phosphorus limited.” All samples analyzed for total phosphorus at site BLB1
(Bayou La Batre at Wintzell Avenue) were below detection limit of 0.05 mg/L. All
samples but one analyzed for total phosphorus from site BLB2 (unnamed tributary to
Bayou La Batre at Little River Road) were below detection limit. One saline water
sample collected in April 2016 had a total phosphorus concentration of 0.063 mg/L. All
samples but one analyzed for total phosphorus from site BLB3 (man-made channel of
Carls Creek at Arnette Street) were below detection limit. The sample collected during
the largest discharge event for the monitoring period had a total phosphorus concentration
of 0.398, which exceeded the 0.05 mg/L criterion. All samples analyzed for total
phosphorus at site BLB4 (natural channel of Carls Creek at Arnette Street) were below
detection limit of 0.05 mg/L.
DISSOLVED OXYGEN
Dissolved oxygen (DO) concentration is an essential constituent that affects the
biological health and the chemical composition of surface waters. Biological processes,
oxidation, and sediment loads all contribute to depletion of DO in surface water. The
ADEM standard for DO in surface water classified as Fish and Wildlife is 5.0 mg/L
except under extreme conditions when it may be as low as 4.0 mg/L. The effects of an
impoundment on DO in the impounded waters and in the downstream release from the
impoundment must be carefully considered in the planning and design stage of a
reservoir project. The equilibrium concentration of DO in water that is in contact with air
is primarily related to water temperature and barometric pressure and secondarily related
to concentrations of other solutes (Hem, 1985). Equilibrium DO in water at 10° C and
25° C is 11.27 mg/L and 8.24 mg/L, respectively. DO concentrations in the project
watersheds are significantly affected by water temperature, stream discharge,
concentrations of organic material in the water, and oxygen-consuming pollutants. These
factors are represented in table 4 where observed DO is compared to the 100 percent
dissolved oxygen saturation for the observed stream temperature for each of the
monitoring periods. Additional DO measurements were made on August 3, 2016 in Carls
Creek tributaries, dominated by wetlands and anastomosing stream channels. Hammar
Creek at 3 Mile Road and Bishop Manor Creek at Argyle Road had DO concentrations of
4.7 and 5.2 mg/L, respectively.
24
Table 4.—Dissolved oxygen measured in monitored streams in the
Bayou La Batre watershed.
Site Dissolved oxygen (mg/L) Average DO saturation
(% atmospheric saturation) Maximum Minimum Average
BLB1 8.3 6.9 7.5 84
BLB2 8.2 6.4 7.3 83
BLB3 9.8 6.4 7.4 80
BLB4 8.3 7.1 7.6 84
CONCLUSIONS AND SOURCES OF WATER-QUALITY IMPACTS
Evaluations of sediment loads, water-quality analyses, land-use data, and aerial
imagery led to conclusions of probable sources of water quality and habitat impairments
in the Bayou La Batre watershed. Stream flow conditions are an important factor that
influences erosion, sediment transport, and attenuation of nutrients and other
contaminants that impact water quality in a watershed. Streams in the Bayou La Batre
watershed are characterized by relatively low gradients, anastomosing channels, forested
flood plains, extensive wetlands, and tidal impacts in the downstream part of the
watershed. The topography of the watershed can be divided into two zones; an upland
headwaters zone and a downstream coastal zone. The upland headwaters zone has
elevations of about 140 ft MSL, 80 ft of relief, and three percent slopes. The average
stream gradient in the upland zone is about 20 ft/mi. The downstream coastal zone part of
the watershed is in the Alabama Coastal Zone and is characterized by extensive wetlands
and marsh, maximum elevation of 25 ft MSL, and an average stream gradient of 7 ft/mi.
Carls Creek splits into two channels just south of Padgett Switch Road (fig. 14).
Site BLB3 is on the man-made relief channel of Carls Creek at Arnette Street. This site
had the highest average turbidity (47 NTUs) and the highest turbidity to discharge ratio
(0.4 NTU/cfs).
Site BLB1 (Bayou La Batre at Wintzell Avenue), had a suspended sediment load
of 22,277 tons per year (t/yr). Site BLB2 (unnamed tributary at Little River Road) and the
combined load for sites BLB3 and BLB4 (Carls Creek at Arnette Street) had suspended
sediment loads of 2,921 and 7,604 t/yr, respectively. Sediment loads normalized to unit
drainage area in the Bayou La Batre watershed are 960 t/mi2/yr for Bayou La Batre site
25
BLB1, 622 t/mi2/yr for site BLB2, and 367 t/mi2/yr for combined sites BLB3 and BLB4.
When the Carls Creek load is subtracted from the load at Bayou La Batre site
BLB1, the remaining load for Bayou La Batre upstream from site BLB1 is 14,673 t/yr
(5,869 t/mi2/yr). Field reconnaissance and research review led to the conclusion that this
surprisingly large suspended sediment load results from three primary sources. The first,
as discussed previously, are estuary streams with tidal influence that have constantly
elevated turbidity and suspended sediment due to movement of water upstream and
downstream in response to tidal cyclicity that mobilizes fine-grained sediment that settled
out in the low gradient estuary zone. Secondly, part of the town of Bayou La Batre storm
water runoff enters Bayou La Batre immediately upstream from the BLB1 site. The third
Figure 14.—Carls Creek channel bifurcation just south of Padgett Switch Road.
Natural channel
Man-made channel
26
source is from three upstream, unnamed tributaries to Bayou La Batre that have relatively
severe bank erosion (fig. 15).
Comparisons of sediment transport rates and water-quality data in watersheds in
Baldwin and Mobile Counties indicate that streams in the Bayou La Batre watershed
have moderate-sized sediment loads and generally good water quality. This is attributed
to the relatively rural setting, extensive wetlands and forests, and use of winter cover
crops on agricultural fields. However, water quality and habitats could be improved and
protected for the future by employing best management practices that prevent destruction
of wetlands, prevent erosion and sediment transport from areas of timber harvesting and
row crop agriculture, and control runoff from urban areas including construction sites and
areas with significant bare and impervious surfaces. Sources of sediment in the Bayou La
Batre watershed include runoff from headwaters row crop agriculture, sand mining
operations, and runoff from urban areas in the town of Bayou La Batre (fig. 15).
Observations recorded during monitoring included at least seven fields used for row crop
agriculture in the headwaters of Bishop Manor and Hammar Creeks have streams or
drainage ditches running through them with no vegetative buffer or sediment detention
(Google Earth, 2016) (fig. 15). One of these streams (unnamed tributary to Hammar
Creek at Tom Waller Road, site BLB8), had the highest turbidity (375 NTU) recorded
during during a storm event in early August 2016 (figs. 15, 16). Other potential sediment
sources are two sand mining operations (fig. 15).
Water samples collected from January through May 2016 at Bayou La Batre
monitoring sites were analyzed for nitrate. The critical nitrate concentration in surface
water for excessive algae growth is 0.5 mg/L. All samples analyzed for nitrate at site
BLB1 (Bayou La Batre at Wintzell Avenue) were below detection limit of 0.3 mg/L. All
samples analyzed for nitrate from site BLB2 (unnamed tributary to Bayou La Batre at
Little River Road) were below detection limit or below the 0.5 mg/L nitrate criterion.
Forty-three percent of analytical results from samples collected at site BLB3 (man-made
channel of Carls Creek at Arnette Street) were below the detection limit, 43 percent were
below the 0.5 mg/L nitrate criterion, and 14 percent exceeded the 0.5 mg/L criterion.
Analytical results for samples collected at site BLB4 (natural channel of Carls Creek at
Arnette Street) indicate that 57 percent are below the detection limit and 29 percent are
below the 0.5 mg/L nitrate criterion, and 14 percent exceeded the 0.5 mg/L criterion.
27
Sand mining
Sand mining
Field
drainage
with no
vegetative
buffer
BLB6 BLB5
BLB3 BLB4
BLB2
BLB1
Stream bank erosion
Bayou La Batre
Figure 15.—Sources of water quality impacts identified by field observations.
28
Water samples collected at Bayou La Batre monitoring sites were also analyzed
for total phosphorus. All samples collected at site BLB1 (Bayou La Batre at Wintzell
Avenue) were below detection limit of 0.05 mg/L. All samples but one analyzed for total
phosphorus from site BLB2 (unnamed tributary to Bayou La Batre at Little River Road)
were below detection limit. One saline water sample collected in April 2016 had a total
phosphorus concentration of 0.063 mg/L. All samples but one analyzed for total
phosphorus from site BLB3 (man-made channel of Carls Creek at Arnette Street) were
below detection limit. The sample collected during the largest discharge event for the
monitoring period had a total phosphorus concentration of 0.398, which exceeded the
0.05 mg/L criterion. All samples analyzed for total phosphorus at site BLB4 (natural
channel of Carls Creek at Arnette Street) were below detection limit of 0.05 mg/L.
Figure 16.—Turbid runoff from row-crop fields in unnamed tributary to Hammar Creek at Tom
Waller Road immediately after a rain event.
29
This assessment indicates that the water quality in the Bayou La Batre watershed
is relatively good, due primarily to the rural character of the watershed and land cover
dominated by forest and wetlands. However, sediment loads are significantly larger than
the geologic erosion rate. Therefore, steps should be taken to correct current impairments
and to protect the watershed from future negative impacts that are common in streams in
Alabama’s coastal region, including urban expansion, timber cutting, poorly maintained
agricultural fields, and conversion of agricultural and forest land to residential
development. One of the primary targets of watershed protection should be preservation
of wetlands and marsh in the Bayou La Batre watershed.
REFERENCES CITED
Cohn, T. A., Caulder D. L., Gilroy E. J., Zynjuk L. D., and Summers, R. M., 1992, The
validity of a simple statistical model for estimating fluvial constituent loads: an
empirical study involving nutrient loads entering Chesapeake Bay: Water
Resources Research, v. 28, p. 2353-2363.
Cook, M. R., and Moss, N. E., 2008, Analysis of water quality, sediment loading,
biological resources, and impacts of land-use change on the D’Olive and
Tiawasee Creek watersheds, Baldwin County, Alabama, 2008: Geological Survey
of Alabama Open-file Report 0811, 140 p.
Cook, M. R., and Moss, N. E., 2012, Analysis of discharge and sediment loading rates in
tributaries of Dog River in the Mobile metropolitan area: Geological Survey of
Alabama Open-file Report 1214, 24 p.
Cook, M. R., Moss, N. E., and Murgulet, Dorina, 2009, Analysis of sediment loading for
the Magnolia River watershed, Baldwin County, Alabama, 2009: Geological
Survey of Alabama Open-file Report 0914, 22 p.
Cook, M. R., and Moss, N. E., Rogers, A. L., Mac McKinney, 2014, Analysis of
sediment loading and water quality for the Bon Secour River watershed, Baldwin
County, Alabama: Geological Survey of Alabama Open-file Report 1409, 34 p.
Eaton, A. D., Clesceri, L. S., and Greenberg, A. E., 1995, Standard methods for the
examination of water and wastewater, 19th edition: Washington, D. C., American
Public Health Association, p. 9-53—9-72.
30
Fondriest Environmental, Inc., 2014, “Turbidity, Total Suspended Solids and Water
Clarity.” Fundamentals of Environmental Measurements. 13 Jun. 2014. Web. <
http://www.fondriest.com/environmental-measurements/parameters/water-
quality/turbidity-total-suspended-solids-water-clarity/ >.
Gali, Rohinth K.; Soupir, Michelle L.; and Helmers, Matthew J., "Electrical Conductivity
as a tool to estimate chemical properties of drainage water quality in the Des
Moines Lobe, Iowa" (2012).Agricultural and Biosystems Engineering Conference
Proceedings and Presentations. Paper 209.
http://lib.dr.iastate.edu/abe_eng_conf/209
Google Earth, 2016, Image of Bayou La Batre watershed, Image date, 1/30/15.
Maidment, D. R., ed., 1993, Handbook of hydrology: New York, Mcgraw-Hill Inc., p.
11.37-11.54.
Mays, L. W., ed., 1996, Water resources handbook: New York, McGraw-Hill, p. 8.3-8.49.
Richards, R. P., 1999, Estimation of pollutant loads in rivers and streams: a guidance
document for NPS programs: Heidelberg College.
U.S. Geological Survey, 2016, StreamStats watershed mapping and statistics, south
Mobile County, Alabama, URL http:// http://water.usgs.gov/osw/streamstats/
accessed July 28, 2016.
31
APPENDIX A
FIELD AND ANALYTICAL DATA
32
Bayou La Batre at North Wintzel Avenue Drainage area=23.2 square miles
Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB1 01/13/16 9:05 439 22,100 8 6.4 13.2 10.4 <0.3 <.05
BLB1 01/21/16 22:40 668 16,700 15 6.0 10 22.0 <0.3 <.05
BLB1 02/15/16 20:45 1,031 15.1 20,800 21 7.3 8.3 12.4 12.0 <0.3 <.05
BLB1 03/11/16 14:10 1,937 19.7 2,650 58 6.9 7.1 1.4 31.2 <0.3 <.05
BLB1 03/28/16 11:15 1,362 21.0 101 25 5.9 7.5 0 6.0 <0.3 <.05
BLB1 04/01/16 14:45 1,473 21.2 709 44 6.5 6.9 0.3 13.6 <0.3 <.05
BLB1 05/31/16 18:10 1,008 28.1 20,100 14 6.9 7.8 12.0 14.0 <0.3 <.05
Unnamed Tributary to Bayou La Batre at Little River Road Drainage area=4.7 square miles Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total
Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB2 01/13/16 8:45 130 18,300 8 6.0 11 10.0 <.3 <.05
BLB2 01/21/16 22:55 198 11,000 16 6.0 6.6 13.6 0.424 <.05
BLB2 02/15/16 21:00 230 15.1 21,700 35 7.0 8.2 13.0 16.8 <.3 <.05
BLB2 03/11/16 14:25 189 19.2 79 30 5.3 7.4 0.0 11.6 <.3 <.05
BLB2 03/28/16 11:30 110 20.9 42 13 4.6 7.5 0.0 7.0 <.3 <.05
BLB2 04/01/16 14:55 150 20.8 52 22 5.5 6.4 0.0 8.4 <.3 <.05
BLB2 05/31/16 18:30 129 29.1 18,700 16 6.7 7.0 11.1 15.2 <.3 0.063
Carls Creek at Arnette Street (man-made channel) Drainage area=17.8
Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB3 01/13/16 8:20 10.3 111 16 5.5 0.07 2 0.399 <.05
BLB3 01/21/16 23:10 444 243 122 6.8 0.1 100.0 0.327 0.398
BLB3 02/15/16 21:15 115 14.9 498 44 6.4 7.4 0.2 18.8 0.559 <.05
BLB3 03/11/16 14:30 180 19.3 39 67 6.4 7.1 0 46.0 <.3 <.05
BLB3 03/28/16 11:40 35 21.0 45 21 6.0 9.8 0 6.0 <.3 <.05
BLB3 04/01/16 15:05 114 20.8 45 48 6.3 6.5 0 18.8 <.3 <.05
BLB3 05/31/16 18:45 17 25.6 630 10 4.3 6.4 0.2 2.0 0.315 <.05
Unnamed Tributary to Bayou La Batre at Arnette Street (natural channel) Drainage area=2.9 square miles Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total
Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB4 01/13/16 8:30 17 112 6 5.6 0.07 2 0.356 <.05
BLB4 01/21/16 23:20 281 1,690 10 5.6 1 6.4 <.3 <.05
BLB4 02/15/16 21:20 75 14.7 110 20 6.4 7.5 0.1 5.6 0.558 <.05
BLB4 03/11/16 14:35 270 19.2 37 42 6.1 7.3 0 26.4 <.3 <.05
BLB4 03/28/16 11:50 205 20.9 42 32 6.3 7.6 0 8.4 <.3 <.05
BLB4 04/01/16 15:15 230 20.9 45 35 6.4 7.1 0 10.8 <.3 <.05
BLB4 05/31/16 18:55 39 25.2 680 5 4.6 8.3 0.3 2.0 0.308 <.05
33
BLB 5 Hammar Creek at 3 mile road
Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB5 8/3/2016 1630 55 25.1 79 44 5.6 4.7 0 24.0 0.509 <.05
Bishop Manor Creek at Argyle Road
Site Date Time Discharge Temp Conductance Turbidity pH DO Salinity TSS Nitrate Total Phosphorus
cfs °C mS/cm NTU mg/L mg/L mg/L mg/L
BLB6 8/3/2016 1650 28 25.2 46 114 6.0 5.2 0 50.0 <.3 0.116
34
GEOLOGICAL SURVEY OF ALABAMA 420 Hackberry Lane
P.O. Box 869999 Tuscaloosa, Alabama 35486-6999
205/349-2852
Berry H. (Nick) Tew, Jr., State Geologist
A list of the printed publications by the Geological Survey of Alabama can be obtained from the Publications Office (205/247-3636) or
through our web site at http://www.gsa.state.al.us.
E-mail: [email protected]
The Geological Survey of Alabama (GSA) makes every effort to collect, provide, and maintain accurate and complete information. However, data acquisition and research are ongoing activities of GSA, and interpretations may be revised as new data are acquired. Therefore, all information made available to the public by GSA should be viewed in that context. Neither the GSA nor any employee thereof makes any warranty, expressed or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report. Conclusions drawn or actions taken on the basis of these data and information are the sole responsibility of the user.
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